Aircraft propeller blade with deicing means



Nov. 23, 1954 R. M. DE wlTT AIRCRAFT PROPELLER BLADE WITH DEICING MEANS Filed June 21, 1951 2 Sheets-Sheet l wm. www@ 1 Sw Mw wv l s M w wm. \1 Q NIH' .N wm. N hm. uw L w.. Nn. NW n |1||||||uhunnunnunuunmwwumnnmmmmmmwwlwmwmhl/ 11111 In: x l.. N .QQ x m. Tr

Nov. 23, 1954 R. M. DE WITT AIRCRAFT PROPELLER BLADE WITH DEICING MEANS 2 Sheets-Sheet 2 Filed June 2l, 1951 JNVENTOR. Haberz ff Dah/ffl' m www2@ bis zzarneys United States Patent Oice 2,695,146 Patented Nov. 23, 1954 AIRCRAFT PROPELLER BLADE WITH DEICING MEANS Robert M. De Witt, Tippecanoe, Ohio, assignor to General Motors Corporation, Detroit, Mich., a corporaion of Delaware Application .lune 21, 1951, Serial No. 232,828

4 Claims. (Cl. 244-134) This invention relates to aircraft propeller blades and means for providing them with ice control by which formation of icing conditions can be forestalled.

The method and `structure consists of providing a groove in the leading edge portion of a blade, -placing an electric heating unit in the groove, and filling the remaining part of the groove with the flat leading edge braze area, such as by metalizing with steel and then regrinding the surface Hush with the leading edge braze area of the blade. The camber sheet is then brazed to the yblade which completely encloses the thermal element. The heating unit is grounded to the blade thus doing away with the need of a return lead. At the yroot portion the electric heating unit is joined to a terminal member .which is insulated from kthe root and the camber sheet.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

Fig. l is a plan view of the propeller blade disclosing the present invention, parts of one of the face members of the blade being broken away for convenience of illustration.

Fig. 2 is an enlarged longitudinal sectional view thru the root portion of the blade substantially as indicated by the line and arrows 2*2 of Fig. 1, the View illustrating one method of providing terminal structure.

Fig. 3 is an enlarged sectional detail of the blade root portion before the heating element is installed, the View being substantially as indicated by the line and arrows 3--3 of Fig. 2.

Fig. 4 is an enlarged and fragmentary view of the portion of the blade member as it is machined or otherwise operated to receive the blade heating element, the View being substantially as indicated by the line and arrows 4 4 of Fig. 1.

Fig. 5 is an enlarged sectional view showing the relation of parts when the heating element is installed and the camber sheet is applied, the view being substantially as indicated by the line and arrows 5 5 of Fig. 1.

Fig. 6 is a longitudinal sectional View on an enlarged scale and substantially as indicated by the line and arrows 6 6 of Fig. 1, the view showing a method of grounding a resistance wire of the heating element.

Fig. 7 is a fragmentary showing of the modified form of blade where the terminal structure of the heating element is situated in the transition portion of the blade or somewhat remote from the root portion.

Fig. 8 is an enlarged sectional detail showing a cavity for reception of the terminal structure of the heating element being substantially as indicated by the line and arrows 8 8 of Fig. 7

Fig. 9 is an enlarged fragmentary View showing the terminal structure in plan View.

Fig. l() is a transverse sectional view in large detail substantially as indicated by the line and arrows 10-10 of Fig. 9.

Fig. 11 is a transverse sectional view of the connector extending between the terminal and heating element substantially as indicated by the line and arrows 11--11 of Fig. 9.

With particular reference to the drawings Figs. 1 to 6 inclusive, 10 refers to a propeller blade of hollow construction comprised of a thrust member 12 and a camber sheet member 14 which when bonded together provide a hollow propeller blade. This particular form of blade comprises a forged thrust vmember 12 having a cylindrical shank portion 16 provided with a retention 8 and a cuff ring 20 circumscribing the same. The thrust member 12 is machined to ,provide va leading edge 22 and a trailing edge 24 with one or more ribs 26 extending from the `root portion 16 to the tip portion V28. The portions of the space between theribs 26 and between the leading edge 22 and trailing edge 24 are machined out to provide hollow structure 30 when the camber sheet 14 is bonded to the leading edge 22, trailing edge 24 and ribs 26. A chamber or recess 32 is machined in the shank portion 16 and a groove 34 is machined inthe surface of the shank 16 and in the leading edge 22 extending from the shank recess 32 to the tip. Within this groove 34 there is disposed an electric heating element 36 whose remote end is grounded at 38. A convenient form of heating element is one that provides a resistance wire 42 embedded in nonconductor 44 contained within a tube 46 which tube 46 has an outside dimension suitably received within the groove 34. The resistance wire 42 is grounded to the closed end 48 of a tube, which tube is in turn grounded to the metal of the blade as at 38. After the heating vunit is placed in the groove 34 by a press t the remaining portion of the groove unilled by the heating unit `is lled with sprayed metal 50 to restore the braze surfaceof the leading edge 22 for juncture with camber sheet 14. This may involve regrinding of the leading edge braze surface in that region where the sprayed metal has been added. After lling and grinding, the leading edge braze surface 22 along with 26 and 24 is coated or otherwise provided for braze union with the camber sheet 14.

The terminal structure for this heating unit 36 is shown in Fig. 2 where the housing tube 46 extends into the chamber 32 and shows a connector wire 52 attached to a terminal ring or washer 54. The terminal 54 is embedded in an insulator 56 fashioned to just tit or till the recess 32. The terminal screw 58 is fastened to the terminal 54 and extends thru an insulator 60 shouldered to be received in an aperture 61 of a clamp ring 62. The clamp ring 62 surrounds the shank of the blade retaining the terminal in place. A pair of nuts 68 are installed on terminal screw 58 by which an electric lead 66 is made available.

In some instances it may not be necessary to associate the heating element with the full length of the blade. Such a construction is shown in Figs. 7 to ll inclusive where the terminal recess 70 is located in a transition portion of the blade 64 between the root 16 and the thrust member 12. A larger groove 72 is machined in the braze surface of the leading edge 22 and projected until it meets the groove 34 heretofore described. The juncture of the recess 70 and larger groove 72 being somewhat as indicated in Fig. 8. In this case the terminal connector 54 joins a conductor 74 embedded in nonconductor 76 contained within a tube 78 that extends thruout the length of the larger groove 72 to a point indicated in Figs. 7, 9 where the conductor 74 joins the resistance wire 42 of the blade heating unit. As before the heating unit is press litted in the groove, and the remaining portion of the groove unoccupied by the blade heating unit is iilled with sprayed metal 50. The surface is ground to preserve continuity with the inside surface of the camber sheet 14 so that when coated and passed thru the brazing cycle the camber sheet will be bonded to the thrust member completely embedding the blade heating unit and its connector.

The terminal connector 54 is likewise supported and enclosed within an insulator 56. Current is conducted from electrical lead 66 to terminal connector 54 thru terminal screw 58 and brass bushing 80 insulated from camber sheet 14 by insulator 60. Terminal screw 58, brass bushing 80 and insulator 60 are placed in an aperture 61 at the inboard end of the camber sheet 14, the same extending toward the root substantially as indicated by the dotted lines 84 in Fig. 7.

With a blade so constructed the electric heating element is entirely enclosed within firm supporting structure where it is thoroughly protected against abrasion, vibration, or

. 3 other injury yet is in good thermal conductive relation with a portion of the blade to be heated. The embedded type of blade heating unit is adaptable to either penodlc energization or continuous energization for preventing the formation of ice upon the blade or for the removal of ice that may have formed thereon. By the appropriate cycling mechanism within or behind the hub structure the thermal elements of the blades can be cyclically energized to maintain the blades free of icing formation.

While the embodiments of the present invention as herein disclosed, constitute a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. A propeller blade for aircraft comprising in combination, a forged thrust member providing a leading edge portion and a cylindrical root portion, means providing a groove in the leading edge portion and root portion, an electric heating element disposed in the groove and having grounded connection with the thrust member at the end of the groove remote from the root, and an outside terminal accessible at the root portion, insulating means surrounding the heating element between the grounded connection and terminal connection, and sprayed metal filling the groove to complete the contour of the leading edge surface and embedding the heating element therein, and a camber sheet secured to the thrust member by bonding along the leading edge so as to com' pletely enclose the blade heating element.

2. The method of installing a thermal element in an airfoil section which comprises: forming a longitudinally extending groove in the leading edge portion of the airfoil section, placing the thermal element in the groove, spraying metal into the remaining portion of the groove so as tocover a portion of the thermal element and embed the thermal element in the airfoil section thereby facilitating the transfer of heat therebetween, and bonding a member to said airfoil section to completely enclose the thermal element.

3. A propeller blade for aircraft comprising in combination, an airfoil section having leading and trailing edge portions, said leading edge portion having a longitudinally extending groove therein, an electrical heating element disposed in said groove, said heating element being embedded in said groove by sprayed metal which fills the remaining portion of the groove to facilitate heat transfer between the heating element and the airfoil section, and a member secured to said leading edge portion to completely enclose said heating element.

4. A propeller blade for aircraft comprising in combination, a thrust member having a root portion and leading and trailing edge portions of thickened structure, one of said edge portions having a groove which extends the length of the blade and connects with a recess in aoY the root portion, an electrical heating element metallically embedded within the groove, a camber sheet bonded to the thrust member and enclosing the heating element, a terminal in said recess, a connector secured to the blade heating element and to the terminal, and an insulator surrounding the terminal and lling the terminal recess, said insulator being formed to continue the original contour of the root portion.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,846,468 Benson Feb. 23, 1932 1,875,454 Havill Sept. 6, 1932 2,248,221 Dornier July 8, 1941 2,402,770 Poekel June 25, 1946 2,464,273 Tanchel Mar. l5, 1949 2,552,075 Van Daam May 8, 1951 2,619,305 Enos Nov. 25, 1952 FOREIGN PATENTS Number Country Date 233,496 Sweden Nov. l, 1944 848,062 France `Tuly 17, 1939 

